The salvage plan for the Arthur J, the 110-foot commercial dredge which sank last week in Lake Huron is being re-evaluated by crews.  The dredge sank to the bottom of the lake about 7 p.m. Tuesday.  Twenty-five percent of the dredge had initially been visible above water.  The decision on when work to salvage the vessel will begin has not yet been made, as the U.S. Coast Guard must approve the salvage plan before work can begin, and the new position of the vessel will likely lengthen the salvage process.  Local beaches continue to be open. Crews are expected to be on hand  to monitor the impact and look for non-hazardous material or debris that might have washed up from the wreck.